1. Field of the Invention
The present invention relates to systems for treating water containing unwanted contaminants. More particularly, the present invention relates to waste water treatment systems including biological media used to aerobically and anaerobically treat solid and liquid waste in the water. Still more particularly, the present invention relates to such treatment systems for large and small-scale waste water systems. The present invention includes novel methods for effectively treating waste water in a way that minimizes the size of the system required to output high-quality, environmentally-suitable, water depleted of ammonia, nitrites, nitrates, perchlorates and other contaminants.
2. Description of the Prior Art
Waste water treatment systems are ubiquitous, from the smallest single-family residence septic system, to industrial facilities for commercial operations and municipalities large and small. It is always the object of such systems to treat for total suspended solids (TSS), biochemical oxygen demand (BOD), nitrogen compounds, E-coli, phosphorous, and virtually any other bacteria, so as to minimize the quantity of such undesirables output by the system. Various well known means have been devised for achieving such goals, with varying degrees of success and efficiency. An overriding general problem, for the most part, with such prior systems has been the scale of operation required to effectively treat that water with high-quality output. That is, for the volumes of water to be treated, the sizes of these systems are correspondingly large. This may be particularly true for relatively small-scale systems, such as single-family residences and small groupings of homes and/or buildings, where coupling to a municipal treatment system may be unsuitable.
In the array of systems designed to treat waste water, many include the use of biological treatments to accelerate the breakdown of solids and the various contaminants associated with waste water. This biological treatment involves the use of microbes having an affinity for the pollutants contained in the water. That is, rather than simply permit solids to slowly decant from the waste water, and then apply a hazardous chemical treatment designed to destroy the pollutants—along with virtually everything else in the water—these microbes are permitted to act upon the waste water. In relative terms, they act to remove the pollutants faster than if nothing were used, and do so without the hazards and difficulties associated with chemical treatment. They must, however, be permitted to reside in some type of holding tank, filter, fixed film or media in order to multiply and feed on the contaminants. Upon completion of their ingestion of the pollutants, the microbes simply die and end up as waste solids that fall to the bottom of the treatment tank or unit for subsequent removal. Some microbes may partially block the availability of surface area or volume resulting in voids of inactivity. The treated water then passes to the next stage, which may simply be some form of a leach bed, or it may be a more complex system, such as a reactor, including, but not limited to, an ultraviolet disinfection means, ozone treatment, or membrane filtration for subsequent transport to a body of water, or for recycling in non-critical uses, such as horticulture.
Unfortunately, while aerobic and anaerobic microbe treatment has significant advantages, it is not exceedingly effective in that it is necessary to provide sufficient “dwell time” or “residence time” for the microbes to “eat” enough of the pollutants so that the waste water is rendered satisfactorily contaminant-free. Of course, the extent to which contaminant removal is satisfactory is a function of governmental regulation. In any case, the volume of water that must be treated can often lead to the need for a rather large-scale treatment unit for a relatively small waste-water-generating facility. As a result, there is often a compromise in the prior systems, which compromise is associated with the contamination-removal requirements, the space available to treat the waste water output, and the cost associated with both. Some of these problems have been addressed by recirculation of the partially treated waste water for repeated treatments. Traditional wastewater treatment systems rely on effective treatment by the gradual accumulation of bacteria. This is common to all treatment schemes but especially pronounced in systems relying on vessels or containers in which air is introduced. Such systems, relying on the gradual accumulation of bacteria for treatment, inevitably will experience failure during hydraulic overload, power failure, temporary shutdown for maintenance or in response to seasonal flows. Often, during such events, the bacteria providing treatment wash through the system and after such an event, treatment efficiency is compromised.
Another problem with such prior systems has been their efficiency over a period of time of use. When the waste water to be treated requires the use of a considerable amount of biological mass, there results a problem of “plugging” of the mass. That is, as waste solids build up on the surface of the mass, or as microbes ingest the pollutants and die they do not always fall to the bottom of the tank. Instead, they become trapped at or near the surface of the mass. This plugging or blocking of the mass significantly reduces the pathways by which subsequent pollutants may pass through to underlying active microbes that are located below the surface of the mass. There are two negative results: 1) the acceleration of pollutant decay caused by microbe ingestion is canceled; and 2) water flow through the mass is reduced and possibly even stopped. It is therefore necessary to either build a substantially larger unit than would otherwise be required—in order to account for this plugging—or to expend the effort to clean the clogged system. Such maintenance may include the introduction of agitation means or the use of pressurized water for removal of dead microbes.
Several prior waste-water treatment systems have been described. These systems have apparently been designed for large- and/or small-scale treatment using biological media to accelerate contaminant reduction. For the most part, they include biological treatment as well as mechanisms designed to enhance the effectiveness of the microbial action. However, each in turn suffers from one or more deficiencies that significantly affect the ability to provide the most effective and relatively inexpensive waste treatment system.
Nitrogen in its oxidized states (e.g. as nitrates or nitrites) can seep into ground waters, causing problems in drinking water. Drinking water standards generally limit the concentration of nitrate to 5 to 10 mg/l, yet effluent from a modern treatment plant may have natural levels greater than 20 mg/l. Nitrogen in its reduced state, as ammonia, is toxic to fish, and severe limits are in effect on many streams to control the maximum concentration.
A conventional method of nitrogen removal is by biological means. With sufficient time, oxygen, and the proper mass of microorganisms, organic nitrogen is biologically converted to ammonia and then further oxidized to nitrate forms. This conversion occurs under aerobic (with oxygen) conditions, and is relatively easy to accomplish, resulting naturally under different known types of waste treatment processes. At this point the nitrogen has not been reduced in concentration, only converted to a different form.
A practical means to remove nitrate is to convert them to nitrogen gas. At this point N.sub.2 will evolve from the water and become atmospheric nitrogen. As atmospheric nitrogen, it is not a water pollutant. Nitrates are best converted to nitrogen gas by microbial action. Under anoxic conditions (without free dissolved oxygen), many common bacteria with a demand for oxygen are able to biochemically remove the oxygen from the nitrate ion, leaving nitrogen gas. This process is called biological denitrification.
For denitrification to occur, the nitrogen must first be converted to nitrates and then the bacteria must have a food source to create a demand for oxygen. This food source may be from outside, like a chemical addition of methanol, by the addition of sewage, or by the natural demand of the organisms (endogenous respiration). This natural demand must occur under conditions where free oxygen is absent.
In the conversion of organic nitrogen and ammonia to nitrates adequate aeration must be provided, and this aerobic process also results in removal of carbon. However, carbon must be present during the denitrification by dentrifying bacteria. Accordingly carbon has to be reintroduced into the system, and this is commonly done by addition of methanol in the art. The biochemical reaction which occurs when methanol is used as the carbon source results in production of nitrogen gas, carbon dioxide and water. The amount of methanol required is about three times the weight of nitrogen compounds to be removed. As is known in the art, other carbon sources can be used.
U.S. Pat. No. 4,005,010 issued to Lunt describes the use of mesh sacks containing the biological medium. The sacks are apparently designed to hold the microbes while allowing fluids to pass through. This unit nevertheless may still result in plugging in that the biological medium will likely become clogged during the course of its usage. Furthermore, the capacity of the unit is directly dependent on the wetted surface area that can be produced for microbial growth. U.S. Pat. No. 4,165,281 Kuriyama et al. describes a waste water treatment system that includes a mat designed to contain the microorganisms. A plurality of mats is disposed vertically and waste water is supposed to pass therethrough. The likelihood of plugging is greater in this unit than in the Lunt device because of the orientation of the mats and the difficulty in maintaining and/or replacing them.
U.S. Pat. No. 4,279,753 issued to Nielson et al. describes the arrangement of a plurality of treatment reactors, alternating from aerobic to anaerobic action. There may be some advantage in using a plurality of small tanks rather than one large tank to achieve the decontamination required in that dwell time is increased; however, this is certainly more costly than is necessary. Moreover, while Nielson indicates that it is necessary to address plugging problems, the technique for doing so is relatively crude and likely not completely effective. U.S. Pat. No. 4,521,311 issued to Fuchs et al. teaches the use of a filtering bed through which the waste water passes and which includes support bedding to suspend the biological medium. The device has a rather complex recirculation process required in order to ensure cleaning of the bedding and the microbes. This device may experience clogging of another sort, and the bedding particles described by Fuchs are required to go through a costly operation for maintenance.
U.S. Pat. No. 5,202,027 issued to Stuth describes a sewage treatment system that includes a buoyant medium in the shape of large hollow balls designed to provide a site for microbial growth. The buoyant balls form but a small portion of the system, which includes a series of complex turbulent mixing sections. The Stuth device is relatively complex and likely requires considerable energy to operate in order to ensure the mixing apparently required.
U.S. Pat. No. 5,221,470 issued to McKinney describes a waste water treatment plant having a final filter made of a sheet of plastic. The sheet of plastic is wrapped about itself so as to form passageways designed for microbe growth. While this design may increase the surface area and, therefore, the dwell time available for microbial action, it is likely that plugging will occur as the passageway will likely fill with dead microbes over a period of time.
U.S. Pat. No. 5,342,522 relates to a method for the treatment of (raw) sewage in a package plant consisting of three bioreactors in series. The treatment is being carried out using three types of biomass. In a first step phosphate is removed by biological means and, at the same time, the chemical and biological oxygen demand is lowered in a highly loaded active sludge system, in a second step a nitrification is carried out, ammonium being converted to nitrate, and in a third step a denitrification is carried out using a carbon source such as methanol or natural gas. The nitrifying and denitrifying bioreactors are both fixed film processes. The thickness of the biofilm on the support material in the nitrifying bioreactor can be influenced by adjusting the aeration system or by adjusting the hydraulic loading. In the denitrifying bioreactor the thickness of the biofilm can be adjusted by raising the shear by means of raising the superficial velocity in the support material. The system according to the invention makes possible effective treatment of raw sewage in a highly loaded system resulting in the far-reaching removal of COD, nitrogen and phosphate. The process can be operated in an alternative mode, where the nitrifying and denitrifying bioreactors are exchanged. The mixing in the nitrifying step is advantageously maintained by aeration under the packages of support material. The denitrifying step was accomplished by means of a propeller stirrer or impeller stirrer, which may be placed centrally in the vessel, was preferably used for active proper mixing. Polacel, reticulated polyurethane or any other carrier material were described as support material for the biomass.
U.S. Pat. No. 5,185,080 describes that in the denitrification chamber, pre-measured quantities of a composite material, containing bacteria and a source of carbon as food, is introduced daily or even bi-daily to the treated wastewater. The bacteria are heterotrophic, laboratory cultured and packaged, as a loose particulate material, capsules, pellets, tablets or other shaped forms. The bacteria Pseudomonas, normally present in the ground, is claimed to be prevalent in this material. The Pseudomonas microorganism has the capability of transforming nitrates to nitrogen gas. The technology of this conversion is well known. The preferred pre-measured microbial tablet includes a carbon supply (source) for biological synthesis. The need for a carbon source is discussed in Handbook of Biological Wastewater Treatment by Henry H. Benjes, Jr., Garland STPM Press, 1980. Denitrification using suspended or fixed growth systems is also discussed in the foregoing reference.
All the above prior art methods attempt to increase the surface area or volume available to microbes for nitrification and denitrification, and thereby increase the productivity of the treatment system.
The above systems are generally referred to as fixed film media or suspended media systems in that surface area for bacteria to grow are provided by the addition of surface. The suspended media bacteria that prefer surfaces would generally predominate such surfaces. However, such surfaces are still subject to failures due to system poisonings and upsets, and may not be easily restarted after such failures, as the surfaces are then contaminated or plugged with dead microbes.
U.S. Pat. No. 4,693,827 describes the addition of a rapidly metabolized soluble or miscible organic material to be added to the carbon consuming step of the process. Heterotrophic organisms consume the added material together with soluble ammonia to generate additional organisms, resulting in the reduction of the soluble ammonia concentration in the wastewater. The rapidly metabolized material comprises one or more short chain aliphatic alcohols, short chain organic acids, aromatic alcohols, aromatics, and short chain carbohydrates.
However, if too much of the rapidly metabolizing material is not introduced in a controlled manner, the heterotrophic organism will proliferate detrimentally. On the other hand if too little is added or in the absence of carbon, the organism will slowly die. Therefore, there is a need for an efficient delivery system for introducing independently carbon and rapidly metabolizing material, bacteria, nutrients and air to such systems. In addition, there is also a need for monitoring the performance of the system as to the extent of the treatment, and feedback from the monitoring detectors to the delivery system for efficient and optimum delivery of carbon, bacteria, nutrients and air.
In U.S. Pat. Nos. 5,863,435 and 6,183,642 issued to Heijen et. al. a method is described for the biological treatment of ammonium-rich wastewater in at least one reactor which involves the wastewater being passed through the said reactor(s) with a population, obtained by natural selection in the absence of sludge retention, in the suspended state of nitrifying and denitrifying bacteria to form, in a first stage with the infeed of oxygen, a nitrite-rich wastewater and by the nitrite-rich wastewater thus obtained being subjected, in a second stage without the infeed of oxygen, to denitrification in the presence of an electron donor of inorganic or organic nature, in such a way that the contact time between the ammonium-rich wastewater and the nitrifying bacteria is at most about two days, and the pH of the medium is controlled between 6.0 and 8.5 and the excess, formed by growth, of nitrifying and denitrifying bacteria and the effluent formed by the denitrification are extracted. In addition the growth rate of the nitrifying and denitrifying bacteria is expediently controlled by means of the retention time, in the reactor, of the wastewater to be treated which is fed in. The electron donor of inorganic nature is selected from the group consisting of hydrogen gas, sulfide, sulfite and iron (III) ions, and said electron donor of organic nature is selected from the group consisting of glucose and organic acids, aldehydes and alcohols having 1–18 carbon atoms. However, such a system could fail based on washouts, introduction of toxic substances, and there will be lag time before the system performs properly. In addition, while organic solvents such as methanol are liquid, and can be introduced as liquid, they are flammable and toxic, and not preferred by many waste water system operators. Lower carbohydrates such as glucose and dextrose while non-toxic, are solids, and require special solid delivery methods to introduce into water treatment systems, and therefore not generally used in the industry. Aqueous solutions of lower carbohydrates may be used; however, such solutions are subject to premature biological degradation, and generally require introduction of antibacterial agents which are harmful for the nitrifiers and denitrifiers.
U.S. Pat. Nos. 4,465,594 and 5,588,777 disclose a wastewater treatment system that use grey water and soaps for denitrification in two different designs of wastewater systems. U.S. Patent application 20020170857 by McGrath et al. published Nov. 21, 2002 discloses the use of a detergent or a detergent like compound for the denitrification of wastewater or nitrified water of U.S. Pat. No. 5,588,777. The application also discloses heating the denitrified wastewater as well as the addition of bacteria to the mixing tank. However, soaps, detergents and detergent like compounds are generally surface active and tend to damage the cell walls of bacteria, adhere to surfaces, interfere with bacterial functions, and are more expensive than methanol. In addition, the metabolism rate of such compounds would be low and would require longer dwell times in the denitrification zones, reactors or media.
Therefore, there is a need for aqueous solution compositions of electron donor or carbon containing material which are non-flammable, liquid, stable to storage, non-toxic to the environment and wastewater microorganisms, readily metabolized, such as carbohydrates and mixtures thereof, and which can be readily introduced to defined locations in wastewater treatment systems to assist in the nitrification and denitrification of wastewaters. In addition, such compositions may also be used for the removal of perchlorates and other pollutants.
The prior art has many examples of teachings that employ bacterial compositions to accomplish, or aid in accomplishing, the biologically mediated purification of wastewater. Hiatt U.S. Pat. No. 6,025,152 describe a methods and mixtures of bacteria for aerobic biological treatment of aqueous systems polluted by nitrogen waste products. Denitrifying bacterial compositions are used in combination with solid column packings in the teachings of Francis, U.S. Pat. No. 4,043,936. These compositions are believed to belong to the family of Pseudomonas. Hater, et al U.S. Pat. No. 4,810,385 teaches a wastewater purification process involving bacterial compositions comprising, in addition to non-ionic surfactants and the lipid degrading enzymes Lipase, three strains of Bacillus subtillis, 3 strains of Pseudomonas aeruginosa, one strain of Pseudomonas stutzeri, one strain of Pseudomonas putida, and one strain of Eschericia hermanii grown on a bran base. Wong, et.al., U.S. Pat. No. 5,284,587 teaches a bacterial composition, that is in combination with enzymes and a gel support is necessary to achieve satisfactory waste treatment. Bacterial species mentioned in Wong et al are Bacillus subtillis, Bacillus licheniformis, Cellulomonas and acinetobacter lwoffi. Similarly, Wong and Lowe, U.S. Pat. No. 4,882,059 teach a process for biological treatment of wastewater comprising bacterial species that aid in the solubilization of the solid debris. The bacterial species used in the teaching of Wong and Lowe are of the following bacterial types: Bacillus amyloliquefaciens and aerobacter aerogenes. These bacterial types are taught to be employed primarily for solubilization and biodegradation of starches, proteins, lipids and cellulose present in the waste product.
Hiatt U.S. Pat. No. 6,025,152 describes the addition of bacterial mixtures in the spore form. Most water treatment systems have residence or dwell times of 2 days or less, and addition of bacteria in the spore form will lead to a substantial portion of bacteria being washed out of the system before it has time to establish, because the environment is not always conducive for bacterial growth.
U.S. Pat. No. 5,185,080 issued to Boyle discloses a system for the treatment of nitrate containing wastewater from home or commercial, not municipal, in which the wastewater is contacted underground by denitrifying bacteria introduced to the treatment zone periodically; the treatment zone being maintained at or above the temperature at which the bacteria are active on a year-round basis by the ground temperature.
U.S. Pat. No. 5,811,289 issued to Lewandowski et al. discloses an aerobic waste pretreatment process which comprises inoculating a milk industry effluent with a mixture of bacteria and yeasts both classes of microorganisms capable of living and growing in symbiosis in the effluent, the population of the bacteria being, in most cases, several times greater than the population of the yeasts, maintaining the temperature and pH of the inoculated effluent between 0.degree. C. and 50.degree. C. and between 1.7 and 9, aerating the effluent while varying, if necessary, the pH at maximum rate of 1.5 pH units per minute and also, if required, modulating the aeration of the inoculated effluent at a maximum rate of 130 micromoles of oxygen per minute.
U.S. Pat. No. 6,077,432 issued to Coppola et al. discloses a method and system for carrying out the bio-degradation of perchlorates, nitrates, hydrolysates and other energetic materials from wastewater, including process groundwater, ion exchange effluent brines, hydrolyzed energetics, drinking water and soil wash waters, which utilizes at least one microaerobic reactor having a controlled microaerobic environment and containing a mixed bacterial culture. It is claimed that using the method of invention, perchlorates, nitrates, hydrolysates and other energetics can be reduced to non-detectable concentrations, in a safe and cost effective manner, using readily available non-toxic low cost nutrients. The temperature of the reactor was maintained at 10 to 42 degrees centigrade.
European Patent Application EP 1151967A1 published Nov. 7, 2001, to Nakamura discloses a liquid microorganism preparation which contains enzymes generated by anaerobic microorganisms, facultative anaerobic microorganisms and aerobic microorganisms will be propagated in a growth tank to make microorganism enzyme water. The obtained enzyme water will be added to a grease trap that retains kitchen water which includes macromolecular organic matter, such as animal and vegetable waste oil, and will be stirred with aeration so that the enzymes and the organic materials will be in contact in order to decompose the organic matter. The decomposition residue and sludge will be separated so as to flow the supernatant water to the sewer pipe.
U.S. Patent application No.2002170857 published Nov. 21, 2002 to McGrath et al. describes a system for nitrified water that comprises a plurality of interconnected tanks including a mixing tank which feeds detention tanks which in combination provide a detention time period for the effluent. A controller determines the amount of detergent dispensed into the mixing tank in accordance with the measured volume of effluent to be treated. The mixing tank comprises a heater for maintaining the nitrified effluent temperature above 50 degrees F. The application also discloses the addition of small doses of bacteria into the mixing tank for denitrification, and heating means to heat the effluent in the mixing tank to accelerate denitrification. An optional line filter can be added to the output of the system for further reducing organic nitrogen concentration. Addition of bacteria or heating means for nitrification was not disclosed, and may be construed as being not necessary for the disclosure.
Therefore, there is a need for bacterial compositions which are not in the spore form or low growth phase, but are in the growth phase when added to the water treatment systems, will continue their growth in the water treatment systems after addition, and delivery means for such addition.
Therefore, there is a need for a waste water treatment apparatus and process that takes advantage of the useful characteristics of biological treatment in an effective manner of existing systems or new systems to be constructed. There is also a need for such an apparatus and process that maximizes the contact between contaminants from the waste water and the microbes without the need for a relatively large processing tank or unit, while providing the best conditions for the microbes to grow. Further, there is a need for an apparatus and process that is simple, energetically efficient, and sufficiently effective to reduce to desirable levels the TSS, BOD, E-Coli, nitrogen-containing compounds, phosphorus-containing compounds, and bacteria of wastewater in a cost-effective manner. In addition, there is a need for a treatment system and apparatus that can deliver microbes and nutrients optimally to enhance the efficiency and performance of the large number of water treatment systems already in operation for nitrification and denitrification without costly reengineering.
There are a large number of existing systems and apparatuses that are not performing efficiently in removing ammonia, nitrite and nitrate which could be made to perform efficiently by the current invention with relatively little cost. In addition, new systems could be made to perform efficiently by following the process described in the present invention.